1 use clippy_utils::diagnostics::span_lint;
2 use clippy_utils::usage::mutated_variables;
3 use clippy_utils::{is_lang_ctor, is_trait_method, path_to_local_id};
5 use rustc_hir::intravisit::{walk_expr, Visitor};
6 use rustc_hir::LangItem::{OptionNone, OptionSome};
7 use rustc_lint::LateContext;
11 use super::UNNECESSARY_FILTER_MAP;
13 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
14 if !is_trait_method(cx, expr, sym::Iterator) {
18 if let hir::ExprKind::Closure(_, _, body_id, ..) = arg.kind {
19 let body = cx.tcx.hir().body(body_id);
20 let arg_id = body.params[0].pat.hir_id;
22 mutated_variables(&body.value, cx).map_or(true, |used_mutably| used_mutably.contains(&arg_id));
24 let (mut found_mapping, mut found_filtering) = check_expression(cx, arg_id, &body.value);
26 let mut return_visitor = ReturnVisitor::new(cx, arg_id);
27 return_visitor.visit_expr(&body.value);
28 found_mapping |= return_visitor.found_mapping;
29 found_filtering |= return_visitor.found_filtering;
31 let sugg = if !found_filtering {
33 } else if !found_mapping && !mutates_arg {
34 let in_ty = cx.typeck_results().node_type(body.params[0].hir_id);
35 match cx.typeck_results().expr_ty(&body.value).kind() {
36 ty::Adt(adt, subst) if cx.tcx.is_diagnostic_item(sym::Option, adt.did) && in_ty == subst.type_at(0) => {
46 UNNECESSARY_FILTER_MAP,
48 &format!("this `.filter_map` can be written more simply using `.{}`", sugg),
53 // returns (found_mapping, found_filtering)
54 fn check_expression<'tcx>(cx: &LateContext<'tcx>, arg_id: hir::HirId, expr: &'tcx hir::Expr<'_>) -> (bool, bool) {
56 hir::ExprKind::Call(func, args) => {
57 if let hir::ExprKind::Path(ref path) = func.kind {
58 if is_lang_ctor(cx, path, OptionSome) {
59 if path_to_local_id(&args[0], arg_id) {
60 return (false, false);
67 hir::ExprKind::Block(block, _) => block
70 .map_or((false, false), |expr| check_expression(cx, arg_id, expr)),
71 hir::ExprKind::Match(_, arms, _) => {
72 let mut found_mapping = false;
73 let mut found_filtering = false;
75 let (m, f) = check_expression(cx, arg_id, arm.body);
79 (found_mapping, found_filtering)
81 // There must be an else_arm or there will be a type error
82 hir::ExprKind::If(_, if_arm, Some(else_arm)) => {
83 let if_check = check_expression(cx, arg_id, if_arm);
84 let else_check = check_expression(cx, arg_id, else_arm);
85 (if_check.0 | else_check.0, if_check.1 | else_check.1)
87 hir::ExprKind::Path(path) if is_lang_ctor(cx, path, OptionNone) => (false, true),
92 struct ReturnVisitor<'a, 'tcx> {
93 cx: &'a LateContext<'tcx>,
95 // Found a non-None return that isn't Some(input)
97 // Found a return that isn't Some
98 found_filtering: bool,
101 impl<'a, 'tcx> ReturnVisitor<'a, 'tcx> {
102 fn new(cx: &'a LateContext<'tcx>, arg_id: hir::HirId) -> ReturnVisitor<'a, 'tcx> {
106 found_mapping: false,
107 found_filtering: false,
112 impl<'a, 'tcx> Visitor<'tcx> for ReturnVisitor<'a, 'tcx> {
113 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
114 if let hir::ExprKind::Ret(Some(expr)) = &expr.kind {
115 let (found_mapping, found_filtering) = check_expression(self.cx, self.arg_id, expr);
116 self.found_mapping |= found_mapping;
117 self.found_filtering |= found_filtering;
119 walk_expr(self, expr);